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Received Nov 3, 2017; Accepted Feb 15, 2018
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1. Introduction
Bronchiectasis is characterised by permanent and abnormal dilation of the lung airways (bronchi). It arises from persistent bacterial airway infection on a background of a deficient immune response. The consequent inflammatory response to infection is largely responsible for the pathology of this condition.
Bronchiectasis is a condition that for many years has had a low profile and had been designated as being an “orphan disease” [1]. However, the widespread availability of high resolution computed tomography (HRCT) scanning has led to a realisation that it is a common condition and a leading cause of respiratory morbidity and mortality. The prevalence of bronchiectasis is not clearly defined. Weycker et al. reported that between 340,000 and 522,000 adults in the US population were receiving treatment for bronchiectasis and that 70,000 adults were newly diagnosed with bronchiectasis in 2013 [2]. Another study reported that there were more than two million adults with bronchiectasis worldwide in 2012 and this was expected to increase to more than three million by 2020 [3]. In addition, it has been recently been recognised that bronchiectasis frequently occurs in patients with chronic obstructive pulmonary disease (COPD). Up to 50% of patients with COPD may have coexistent bronchiectasis [4–6].
From the immunology point of view, bronchiectasis is of significant interest as it provides insights into both mechanisms of immune deficiency and the consequent persistent inflammatory response to bacterial infection. It also provides a potential opportunity to manipulate the immune response to improve patient outcome. It should be emphasised that there are a wide variety of factors that may contribute to the development of bronchiectasis and the pathogenesis is still not fully understood (Table 1).
Table 1
Important predisposing causes for bronchiectasis.
| Postinfective |
| Childhood infection: pneumonia, measles, whooping cough |
| Tuberculosis |
| Viral infection: HIV, HTLV-1 |
| Immune deficiency |
| Humoral immunity: CVID, X-linked agammaglobulinaemia |
| ?IgG subclass |
| Transporter associated with antigen processing deficiency |
| Mannose binding lectin deficiency |
| Hyper-IgE syndrome |
| Chronic granulomatous disease |
| Malignancy |
| Mucociliary function |
| Ciliary dyskinesia |
| Systemic inflammatory disease |
| Rheumatoid arthritis |
| Other arthritic disorders |
| Inflammatory bowel disease |
| Airway obstruction |
| Foreign... |